<!doctype html>
<html lang="en">

<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=1">
    <title>Clear Fix</title>
    <style>
        .box1{
            width: 200px;
            height: 200px;
            background-color: #bfa;
        }
        /* .box1::before{
            content: "";
            display: table;
        } */
        .box2{
            width: 100px;
            height: 100px;
            background-color: orange;
            margin-top: 100px;
        }
        /* clear fix,可以同时解决高度塌陷和外边距重叠问题 */
        .clearfix::before,.clearfix::after{
            content: "";
            display: table;
            clear: both;
        }
    </style>
</head>
<!-- 高度塌陷的解决方案 -->
<body>
    <div class="box1 clearfix">
        <div class="box2"></div>
    </div>
</body>

</html>